Steam for Linux

I purchased "Spec Ops: The Line" from getgamesgo. When I used the key on the Linux Steam client, it told me the key was for "Cogs", and that it's already activated on my account (because I do have Cogs, and it's already installed).

I tried the same key on the Windows Steam client, and it correctly activated "Spec Ops: The Line".

I'm absolutely positive it's the same key, because I didn't type it in either case--I copy/pasted it from my email. PM me if you want the key in question to investigate.

Yep, positive. Steam even recognized it and thought it was for Cogs! My cogs key isn't even in my email account (it's on my humble store account page), so there's no way I could've copied that by mistake.